1. Field of Disclosure
This invention relates to coastal protection from storm surges to reduce coastal flooding.
2. Background
Flooding in coastal areas resulting from tropical storms, hurricanes, cyclones or typhoons produces death and destruction. Storm surge is the major cause of flooding. Storm surge is water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge can combine with normal tides to create a storm tide, which can increase the mean water level 15 feet or more. In addition, wind driven waves are superimposed on the storm tide. A surge is not generally one hill of a high sea level; it generally is a series of ever growing hills of high sea levels.
Storm surge is particularly dangerous along coastlines that do not rise significantly above mean sea level, such as the densely populated Atlantic and Gulf Coasts of the United States that lie less than about 10 feet above mean sea level for miles inshore (mean sea level is halfway between mean high and low tides). Urbanized coastal areas often employ a shoreline wave barrier such as a bulkhead or seawall to prevent destruction of beachfront properties by wind driven waves. Galveston, Tex. installed a 17 feet tall concrete seawall, 16 feet wide at the base, and now ten miles long, after the great hurricane of 1900 that killed 6000 people and destroyed the city.
In September 2007, Hurricane Ike made landfall near the north end of Galveston Island. Storm surges of 15-20 feet above normal tide levels occurred along the Bolivar Peninsula of Texas and in much of the Galveston Bay area. At Sabine Pass east of Galveston Island, the storm surge was recorded at 22 feet above mean sea level. Preceded by large plunging waves breaking over the Galveston seawall, the ensuing storm surges overtopped the seawall, inundating the town. Property damage from Ike is estimated at approximately $10 billion with nearly 200 people killed.
As a result of the Ike catastrophe at Galveston, proposals (called the “Ike Dike”) have been advanced to extend the Galveston seawall to 60 miles at the same height and to erect a flood gate—modeled from the Maeslantkering storm surge barrier across the Rotterdam channel in the Netherlands—to close off a nearly two mile stretch of open water between Galveston Island and Bolivar Peninsula to protect Galveston Bay from a storm surge. The cost of such a massive solution would be billions of dollars. However, even the existing Galveston seawall was overtopped by the Hurricane Ike.
Steel or concrete walls permanently installed atop wave barriers such as seawalls, bulkheads, dikes, or levees to prevent overtopping from storm surges offer a potential solution. However, permanent walls parallel to the shoreline and tall enough to block and withstand a storm surge obscure the view of the waterscape, mar the landscape of often-beautiful coastline areas, and impede recreational use of the beaches. U.S. Pat. No. 7,033,122 addresses this and describes a folded metal wall situated in an accommodation space in a dike that can be unfolded and locked in place by workers in advance of an anticipated storm surge. However this solution requires human intervention to erect, and men, machines and electrical power may not be available to erect the walls when the time comes, such as, for example, if workers are unable to get to assigned stations due to storm conditions or if mandatory evacuation has been instituted or if power outages have occurred rendering machines unworkable.
U.S. Pat. No. 6,338,594 describes protecting dikes from overtopping by vertically elevating buoyant walls from an underground chamber into which water is pumped to float the walls upwardly, but these kinds of solutions depend on expensive pumping stations and are susceptible to inoperability from power outages. Use of rising storm waters to fill underground chambers and buoy walls vertically upwardly atop a dike or bulkhead is described in U.S. Pat. Nos. 5,725,326 and 7,744,310. Riverbanks have been described lined by self-elevating stanchions using interconnected flexible sheeting between stanchions to provide a water containment barrier. See U.S. Pat. No. 4,377,352.
Doors and other grade level openings in a building or wall have been guarded from entrance of flooding water by self-actuating buoyant gates that require no power and rotate upwardly about a horizontal axis to barricade the opening against water. See U.S. Pat. No. 6,623,209, by the instant inventor.
Relatively inexpensive self-actuating buoyant gates that require no power and rotate upwardly, of the type taught in U.S. Pat. No. 6,623,209 by the instant inventor have not been used to protect land from storm surges that accompany a hurricane or tropical storm. A problem with use of a type of gate taught in U.S. Pat. No. 6,623,209 to relatively inexpensively protect against storm surge overtopping a wave barrier wall is that the rush and ebb of strong waves overtopping the barrier wall in advance of arrival of the series of storm surges is ineffective to raise and maintain the gate fully upright to oppose the storm surges. If overtopping water is enough to raise from horizontal, and even momentarily drive the gate relatively upright, the wave quickly recedes, pressure against the face of the gate drops drastically, and the gate falls down.
A low cost solution remains needed for bulkheads, seawalls, levees, dikes or other shore line water barrier walls susceptible to storm surge overtopping. The solution desirably is one that, without requiring human intervention or electrical power, erects a storm surge barrier at or on the shore line water barrier wall in advance of arrival of a storm surge, to protect the shore behind the shore line water barrier wall from flooding caused by a storm surge overtopping the shore line water barrier wall. The solution desirably would be one that, when not in use, does not block the view of the waterscape of the body of water lined by the bulkhead, seawall, levee, dike or other shore line water barrier wall.